1. Field of the Present Invention
The present invention relates to the field of disc brakes, and more particularly to an automotive disc with reduced noise, reduced vibration and less eccentric wear on the brake pads.
2. Discussion of the Related Art
Previously, a disc brake has been described having a structure where a braking torque generated by an outer pad is transmitted to a stationary portion of a vehicle through a caliper, and the braking torque of an inner pad is transmitted to a support member, as disclosed, for example, in Japanese Utility Model Publication No. 62-130233. As shown in FIGS. 5A and 5B, such a disc brake has a caliper 2, which is positioned around a rotor 1. The caliper 2 is movable with respect to a support member 3 in an axial direction of the rotor 1 through a pair of guide pins 4 and 5. A hydraulic cylinder mounted on the inner side of the caliper 2 is operated to press the inner pad 6 against the rotor 1. When the caliper 2 is moved by the reaction force of the rotor 1 during a pressing operation, a claw 7 on the outer side of the caliper 2 presses the outer pad 8 against the rotor 1. In this case, the outer pad 8 is connected to the caliper claw 7 by a projection and recess engagement 9, so that the braking torque of the outer pad 8 is transmitted to the caliper claw 7.
In this disc brake, the braking torque of the inner pad 6 is transmitted to the support member 3. The braking torque of the outer pad 8 is transmitted to the rotor run-in side guide pin 4 through the caliper claw 7, and then to the body of the vehicle. Therefore, in a conventional structure the guide pin arrangement consists of a large-diameter main guide pin 4 on the rotor run-in side portion, and a sub-guide pin 5 on the rotor run-out side portion with a small diameter so as to allow for manufacturing tolerances. Moreover, the braking torque of the outer pad 8 is transmitted through the main guide pin 4 having a large diameter.
The braking torque of the outer pad 8 is transmitted to the caliper 2 which can move in the axial direction of the rotor 1. The caliper 2 has an arm which extends from the side of the caliper 2 to face the support member 3 at a position in the stationary portion of the vehicle. The guide pin 5 is attached to the support member, and is inserted through the caliper arm. The guide pin 5 is located on the inner side of the rotor 1, and the caliper 2, supported by the guide pin 5, holds the outer pad 8 using the claw 7, which extends to the outer side of the rotor 1.
Therefore, when the outer pad 8 is pressed against the rotor 1, it generates a moment M for counterclockwise rotation of the outer pad 8, as shown in FIGS. 5A and 5B, such that the main guide pin 4 serves as the base point. Thus, the overall body of the caliper 2 is deformed, and the inner pad 6 and the outer pad 8 are not pressed against the rotor 1 in parallel. This causes eccentric wear of the inner pad 6 and the outer pad 8.
When the braking torque is generated, the main guide pin 4 transmits the torque to the support member 3. Although a rubber bushing is mounted on the smaller-diameter sub-guide pin 5, the rubber bushing can become deformed when the braking torque is generated. Therefore, the caliper 2 and the support member 3 vibrate due to the generation of the moment M. This, in turn, causes noise.